1. Field of the Invention
This invention relates to electrochromic elements and more particularly electrochromic elements which are useful as light controllable windows for buildings, automobiles and passenger vehicles and various types of light controllable glasses to be used for indoor decoration or partitions; display devices; and anti-dazzle mirrors for automobiles and other vehicles.
2. Description of the Prior Art
A conventional electrochromic device such as a light controllable glass of conventional type as disclosed in Japanese Patent Laid-Open Publication No. 63-18336 is known which glass comprises a chromogenic material in the form of a film obtained by sputtering or vacuum-depositing an inorganic oxide such as tungsten oxide (WO.sub.3) over a transparent electrically conductive film.
3 . Problems to be solved
However, the conventional film formation techniques must be carried out under vacuum, resulting in increased production costs and a requirement of a large size vacuum apparatus if an electrochromic element of a large area is intended to be produced. Furthermore, since a substrate is heated at an elevated temperature during sputtering, it is necessary to select certain conditions if a substrate other than a glass, such as synthetic resin-made substrate is used, resulting in difficulties in lightening an electrochromic element.
There is also a problem that tungsten oxide can only make an electrochromic element exhibit blue color.